JP-A-10-293460 proposes a related art process cartridge that has a developing roller and can be attached to and detached from an image forming apparatus. Such a related art process cartridge includes a process body including the developing roller and a related art developer container that can be attached to and detached from the process body. The developer container contains a developer therein and supplies the developer to the process body. The related art developer container includes a developer supply port formed in a container body and a supply port shielding member for opening and closing the developer supply port so as to supply the developer to the process body.